C2123 – Data from transmitter ID 3 not received (main) (Lexus)

Lexus-specific code — factory diagnostic data

C2123 means the tire pressure warning system on your Lexus CT200h stopped hearing from one tire pressure sensor. In real life, you may see the TPMS warning light and lose pressure readings for one tire, even though the tire is fine. This is a Lexus manufacturer-specific chassis code, so the exact logic can vary by platform. According to Lexus factory diagnostic data, this code indicates “Data from transmitter ID 3 not received (main).” That wording points to a missing radio message from a registered transmitter, not an automatic confirmation that a sensor failed.

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C2123 Quick Answer

The Tire Pressure Monitor ECU did not receive the expected data message from transmitter ID 3. Diagnose it as a “missing TPMS sensor signal” problem until tests prove the root cause.

What Does C2123 Mean?

Official definition: “Data from transmitter ID 3 not received (main).” In plain terms, the tire pressure monitor module expects regular updates from a specific registered sensor ID, and it did not get them. That usually triggers a TPMS warning and prevents accurate monitoring for that position in the ECU’s memory.

What the module checks and why it matters: The TPMS ECU “listens” for a valid RF transmission that matches the stored ID slot labeled “ID 3” in the main wheel set. It checks message timing, validity, and ID match. The code tells you which stored ID slot went silent. It does not tell you why it went silent. Treat C2123 as a direction to verify the sensor’s transmission, the ECU’s ability to receive RF, and the stored ID registration for the CT200h.

Theory of Operation

Under normal operation, each wheel-mounted TPMS transmitter sends a coded RF message that includes its unique ID and pressure data. The Tire Pressure Monitor ECU receives those messages, validates the IDs against its stored “main” set, and then updates pressure status and warning logic.

C2123 sets when the ECU does not receive a valid message from the stored ID 3 within its expected time window. A dead sensor battery can cause it. Wrong ID registration can cause it, too. RF reception problems also matter on Lexus platforms, especially after body work or an ECU/power issue that changes what the module expects.

Symptoms

These are the most common signs you will notice with C2123 on a Lexus CT200h.

• Scan tool behavior TPMS data for one registered ID shows “not received,” “no data,” or updates intermittently.
• TPMS warning Tire pressure warning light stays on or flashes and then stays on.
• Missing tire reading One tire’s pressure will not display or will not update, if the vehicle shows individual readings.
• Intermittent operation The warning may come and go after driving, especially with temperature changes.
• After tire service The fault appears after a tire rotation, tire replacement, or wheel swap.
• After ID registration The fault appears after a TPMS relearn or transmitter ID programming event.
• Multiple TPMS codes Other “transmitter not received” codes may appear if more than one sensor drops out.

Common Causes

• Incorrect TPMS transmitter ID registration for “ID 3”: The tire pressure monitor cannot match received RF data to the stored ID 3, so it flags “data not received” for that slot.
• Low transmitter battery or internal transmitter fault: A weak or failed sensor transmits intermittently or not at all, so the main receiver never receives valid frames for ID 3.
• Wheel set mismatch or uninitialized second wheel set logic: If the vehicle expects a different stored set, the module listens for IDs that are not present on the car.
• RF interference or poor reception at the TPMS receiver path: Strong nearby RF noise or a reception problem reduces message quality until the module stops accepting frames as valid.
• Damage to TPMS receiver/antenna harness or connector: Corrosion, pin fit issues, or an open in the receiver circuit reduces sensitivity and prevents reliable reception of ID 3 data.
• Power or ground integrity issue at the tire pressure monitor system: High resistance in power feeds or grounds can reset the receiver or degrade processing, which interrupts ID decoding.
• Related TPMS DTCs masking the root problem: A separate fault in the tire pressure monitor system can stop normal ID processing, and C2123 becomes a secondary symptom.
• Aftermarket equipment causing intermittent electrical or RF noise: Poorly filtered chargers, inverters, or add-on modules can introduce noise that disrupts TPMS reception or module stability.

Diagnosis Steps

You need a scan tool that can access the Lexus tire pressure monitor module and show TPMS Data List items. Use a quality DVOM for fuse, power, and voltage-drop checks. A TPMS activation tool helps confirm a sensor transmits, but do not treat it as proof of correct ID registration. Have basic backprobing tools and service information for connector locations.

1. Confirm C2123 in the tire pressure monitor module. Record stored, pending, and history codes. Save freeze frame data, focusing on ignition state, vehicle speed, system voltage, and any related TPMS DTCs present at the same time.
2. Check module presence on the scan tool network list and verify you can communicate with the tire pressure monitor module reliably. If communication drops, address power/ground or network issues first. Then inspect fuses and power distribution that feed the TPMS system before probing any module connector.
3. Verify tire pressure monitor power and ground under load. Do voltage-drop testing with the circuit operating, not continuity. Target less than 0.1 V drop on the ground path, and confirm the power feed holds steady while the module runs.
4. Run a visual inspection of the TPMS-related harnesses and connectors you can access. Focus on water intrusion, green corrosion, pushed pins, loose terminal drag, and harness pinch points. Pay extra attention to any receiver/antenna connectors if the platform uses them.
5. Use the scan tool Data List to look for ID status and reception counters. Compare “transmitter ID 3” data to the other IDs that report normally. Note whether ID 3 shows no reception at all, intermittent reception, or unrealistic pressure/temperature values before dropping out.
6. Verify the vehicle configuration that the module expects. Check whether the system supports multiple wheel ID sets and whether the correct set is selected. If the TPMS module expects a different set, it will “not receive” the IDs currently installed.
7. Confirm correct ID registration for the “ID 3” slot using the scan tool utility or service procedure. Do not assume “ID 3” equals a specific wheel position. If IDs were entered manually, recheck for transposed digits or incorrect characters.
8. Use a TPMS activation tool to trigger each wheel sensor and observe scan tool response. Compare the triggered sensor’s ID to what the module stores in the ID 3 slot. If the tool shows a sensor transmits but the module never acknowledges it, suspect registration, reception, or module-side issues.
9. If reception issues look likely, isolate interference. Remove power from common noise sources one at a time, such as chargers and inverters. Then road test and capture a scan tool snapshot during the event. Remember the difference: freeze frame shows conditions when the DTC set, while a snapshot captures intermittent reception loss during your test.
10. Clear DTCs and perform a verification drive. Watch for a pending versus confirmed/stored return. Many Lexus chassis-related faults can act like Type B logic, so one failure may set pending first, while a repeated failure stores the code on the next drive cycle.
11. If C2123 returns quickly after clearing, recheck power/ground integrity and connector pin fit. A hard fault often returns at key-on when the module runs its checks. If the code only returns after driving, focus on intermittent transmitter output, temperature-related sensor failure, or reception issues.

Professional tip: When the scan tool shows three IDs updating and one slot dead, treat it as a “system can receive, but not this ID” problem first. That pattern usually points to ID programming, a mismatched wheel set, or a weak transmitter. Still prove power and ground quality with voltage-drop tests before you condemn any sensor or receiver.

Possible Fixes

• Register the correct transmitter ID into the ID 3 slot: Correct the stored ID, then perform the Lexus initialization/learn procedure and confirm live data updates.
• Select the correct wheel ID set and re-initialize if equipped: Match the active set to the wheels installed so the module listens for the correct IDs.
• Repair power, ground, or fuse feed issues found during voltage-drop testing: Restore clean power delivery and a low-resistance ground path to prevent resets and reception loss.
• Clean, repair, or re-pin affected connectors and harness sections: Fix corrosion, poor terminal tension, or wiring damage that reduces receiver performance.
• Replace the TPMS transmitter only after confirming it fails transmit/ID validation: Verify the sensor does not respond reliably or does not match the stored ID before replacement.
• Address RF/electrical interference sources after proving they correlate to the fault: Remove or re-route noisy accessories and confirm C2123 does not return.

Can I Still Drive With C2123?

You can usually drive your Lexus CT200h with C2123, but you should treat it as a safety-related warning. This code means the tire pressure monitor module stopped receiving data from transmitter ID 3 (main). When that transmitter stops reporting, the system cannot reliably warn you about a low tire for that wheel position. The vehicle will still steer, brake, and accelerate normally in most cases. However, you lose early warning for a leak, overheating tire, or underinflation. Check and set tire pressures with an accurate gauge before driving. If the TPMS warning flashes first, or the light returns quickly after clearing, diagnose it soon.

How Serious Is This Code?

C2123 ranges from an inconvenience to a legitimate safety concern. It becomes “mostly inconvenience” when you confirm all tires hold pressure and the warning stays on steady. It becomes more serious when you cannot confirm tire condition, when you travel at highway speeds, or when temperatures change quickly. Underinflation increases stopping distance and heat. It also increases the chance of tire failure. This DTC does not prove a bad sensor. The message only points to a communication loss from one registered transmitter. You must confirm the root cause with scan data and circuit checks before replacing parts.

Common Misdiagnoses

Technicians often replace a sensor immediately because the code mentions a “transmitter.” That wastes money when the real issue sits in the wrong ID registration, a wheel set mismatch, or a marginal receiver path. Another common error involves assuming “ID 3” equals a specific corner. Lexus assigns IDs during registration, so ID numbering does not guarantee location. Shops also skip checking freeze frame and current data, then miss an intermittent drop-out caused by corrosion at a TPMS antenna/receiver connector or a disturbed harness after body work. Avoid guesswork. Confirm which transmitter fails to report, then verify registration, power/ground integrity, and connector condition.

Most Likely Fix

The most common confirmed repair directions for C2123 on Lexus platforms involve restoring communication from the correct registered transmitter. Start by verifying the TPMS IDs stored in the tire pressure monitor and confirming which transmitter does not report in live data. If the transmitter ID list does not match the wheels installed, perform correct ID registration and initialization with a capable scan tool. If IDs match but ID 3 never reports, inspect for sensor damage, incorrect wheel build, or a dead sensor battery. Only after you verify those basics should you pursue receiver/antenna harness checks or module-side circuit diagnosis.

Repair Costs

Repair cost depends on whether the confirmed root cause is wiring, connector condition, a sensor, a module, or the labor needed to diagnose the fault correctly.

Last updated: April 8, 2026

Definition source: Lexus factory description · Autel MaxiSys Ultra & EV. Diagnostic guidance is based on factory-defined fault logic for this code.